مقايسه آسيب شنوايي ناشي از نويز و ضربه صوتي

A comparison between noise-and acoustic trauma-induced hearing loss

Objective: Exposure to excessive noise can cause physiological variations in auditory system. These changes may manifest as hearing loss (HL), tinnitus and even vertigo. The aim of this investigation was to compare the degree of hearing impairments among workers in Ahvaz Steel Factory with those exposed to artillery shell explosions during the imposed war. Subjects and Methods: In this analytical study, 400 adults with hearing impaired, aged 20-40 years, were studies and divided two groups: acoustic trauma (AT) and noise-induced hearing loss (NIHL). After otorhinolaryngology inspections, otoscopy, pure tone audiometry, speech audiometry and tympanometry evaluations were performed for all participants. Data analysis was performed by SPSS software and 0.05 value was regard as a significant level. Results: Hearing impairment in NIHL and AT groups was symmetrical in 91 % and 68 % of clients; respectively. The severity of hearing loss in AT group was significantly higher than NIHL group (P<0.05). The resultant hearing problem in NIHL subjects was seen predominantly in 2000-8000 Hz region. While in AT subjects, it was located in 3000-6000 region. We found a significant correlation between the degree of hearing loss and sound intensity level (P<0.05, r =0.085). A large number of subjects in AT group had tympanic membrane perforation and ossicular chain disruption. Conclusion: Exposure to high intensity sounds, even during a brief period, may cause an irreversible damage in auditory system. These damages are more intense when subject expose to impulse noise than when he experiences a steady noise, such as in workplace noise.